R language-missing parameters and no default values

"Missing parameter, no default value"-- in the R language Self-coding function, the error is reported if the parameter has no input value.

1. Questions

For example:

> My.func
My.func<-function (p) {
Print ("TEST is ok!")
Print (P)
}
> My.func ()
[1] "TEST is ok!"
Error in print (p):

Evaluating the ' x ' parameter when selecting a method for the ' print ' function error: Errors: Missing parameter ' P ' and no default value

2. Analysis

What about this? Is it possible to add null values as in the Java language? For example:

My.func<-function (p) {
Print ("TEST is ok!")
if (Is.null (p))
Print ("p value is null.")
Else
Print (P)
}

The answer is no. This is really not the same as other object-oriented languages like Java.

So how to solve it?

3. Solve

The answer is to add the default parameters, that is, in the R language, there are no indeterminate parameters to be allowed.

Examples of improvements:

My.func<-function (p=1) {
Print ("TEST is ok!")
Print (P)
}

Run:

> My.func ()
[1] "TEST is ok!"
[1] 1
>
After you set the default value, it works even if you do not enter a parameter.

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

R language-missing parameters and no default values